<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>JS打字小游戏</title>
    <style>
        body {
            padding: 0;
            margin: 0;
        }

        #gameStage {
            width: 100%;
            height: 1000px;
            background-color: aquamarine;
        }
      #box{
        position: absolute;
        margin: 20px 20px;
        width: 300px;
        height: 80px;
        line-height: 80px;
        background-color: yellow;
        text-align: center;
        border-radius: 8px;
        z-index: 99;
        opacity: 0.8;
      }
      #box span{
        font-size: 45px;
        color: red;
      }
    </style>
</head>
<body>
<div id="gameStage">
  <div id="box">
    <span>得分:</span>
    <span id="score"></span>
  </div>
</div>

<script>
  /**
   * 字母
   * @param id
   * @param alphabet
   * @param posX
   * @param posY
   * @param size
   * @constructor
   */
  function Word(id, alphabet, posX, posY, size) {

    //初始化数据
    this.id = id || '';
    this.alphabet = alphabet || 'a';
    this.posX = posX || 0;
    this.posY = posY || 0;
    this.size = size || 64;


    // 新建
    this.create = function () {
      var str = '<span class="word" id="alphabet-' + this.id + '">' + this.alphabet + '</span>';
      var gameStage = document.getElementById('gameStage');
      gameStage.innerHTML += str;

      var divNode = document.getElementById('alphabet-' + this.id);
      divNode.style.position = 'absolute';
      divNode.style.fontSize = this.size + 'px';
      divNode.style.left = this.posX + 'px';
      divNode.style.top = this.posY + 'px';

    };

    // 重置.
    this.reset = function () {
      var divNode = document.getElementById('alphabet-' + this.id);
      divNode.style.display = 'none';
      this.moveTo(0, 0);
    };

    // 移动到指定点
    this.moveTo = function (posX, posY) {
      this.posX = posX;
      this.posY = posY;

      var divNode = document.getElementById('alphabet-' + this.id);
      divNode.style.left = posX + 'px';
      divNode.style.top = posY + 'px';
    };

  }

  /**
   * 导演类
   */
  var director = {
    alphabets: ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'],

    nodes: new Array(),

    /**
     * 逐帧运行
     */
    runFrame: function () {

      //更新已经产生所有点的坐标
      for (var index in this.nodes) {
        var node = this.nodes[index];
        if (node) {
          node.moveTo(node.posX, node.posY + 5);
          if(node.posY>window.innerHeight-65){
            director.stop();
          }
        }
      }

      //随机产生字母
      var r = Math.floor(Math.random() * this.alphabets.length);
      var w = new Word(new Date().getTime(), this.alphabets[r]);

      w.create();
      this.nodes.push(w);

      var posX = Math.floor(Math.random() * window.innerWidth);
      if (posX < 50) {
        posX = 100;
      }
      if (posX >= window.innerWidth - 100) {
        posX = window.innerWidth - 100;
      }

      w.moveTo(posX, 0);


    },

    /**
     * 开始游戏
     */
    start: function () {
      var _this = this;

      //监听键盘事件
      document.onkeydown = function () {
        var alphabet = String.fromCharCode(event.keyCode); //获取键盘敲中的字母
        var flag=false;
        for (var i = 0, len = _this.nodes.length; i < len; i++) {
          if(!_this.nodes[i]) {
            continue;
          }
          if (alphabet === _this.nodes[i].alphabet) {
            _this.nodes[i].reset();
            scoreCounter.incScore();
            _this.nodes[i] = null;

            flag=true;
          }
          view.show();
        }
        if(!flag){
          scoreCounter.decScore();
          view.show();
        }


      };

      //游戏主循环
      Timer=setInterval(function () {
        _this.runFrame();
      }, 200);

    },

    stop: function () {
      clearInterval(Timer);
    }

  };

  /**
   * 计分器
   */
  var scoreCounter = {
    score: 0,
    incScore: function () {
      this.score++;
    },
    decScore:function(){
      this.score--;
    },

    getScore: function () {
      return this.score;
    }
  };

  var view={
    show:function(){
      document.getElementById("score").innerHTML=scoreCounter.getScore();
    }
  };


    director.start();



</script>
</body>
</html>